Process for surface-hardening metal.



' ment of a temperature of about 6000 deperature in practice venien'tsupport and the JOHN H. MQCORMICK,

or c oLumBus, 01110.

r'aocnss roe suarAon-nmmnmue METAL.

No Drawing.

Specification of Letters Patent. Application filed May as, 1910. SerialNo. 582,799.

Patented Sept. 2, 1913.

To all whom it may concern.

Be it known that I, JOHN H. MoConMIoK, a citizen of the United States,residing at Columbus, in the county of Franklin and State of Ohio, haveinvented certain new and useful Improvements in Processes forSurface-Hardening Metal, of which the following is a specification.

My invention. consists in an improved process whereby malleable andsimilar iron and steel, containing a necessary amount of free orcombined carbon, ma be surface hardened to a desired depth withoutchanging the character of the interior or main body of the metal; toaccomplish this object in a simple, rapid and convenient manner and toadmit of the hardening of a portion only or the whole of the surface ofa metal body.

To this end, my process consists in apply ing to the surface to behardened, the flame produced by ignitin oxygen and acetylene gases inany desirab e proportions to attain a flame of very intense heat, or tootherwise subject the surface to a very intense heat to very rapidlybring the surface against which the heat is directed, to a hardcnintemperature before the body metal un er the surface against which theflame is directed, has reached this temperature, and then quicklychilling the same before the interior of the body metal is heated byconduction. It will thus be noted that I employ heating means of highintensity to very rapidly bring the surface metal to be hardened to thecorrect hardening temperature which has been variously estimated to bebetween 1300 and 1500 degrees F., but which temis usually determined bythe eye when the metal has reached what is known in the art as'a cherryred. In a number of the claims, I have referred to the hardeningtemperature by which I mean that the surface metal has reached atempering heat, or, in other words, it is at a cherry red. I

In carrying out this process, it has been found that it is necessary tosubject the article to be surface hardened, to a temperature of over4000 degrees Fahrenheit, the best results being obtained by theemploygrees. In carrying out this. rocess, the metal body, the surfaceof whichis to be treated, may be given any suitable or conflame directeddition existing before to the metal surface thereon from any suitable orwell known form of burner or nozzle which is carried at the end of a gasconducting hose or pipe. The surface of the body belng sufficientlyheated, the flame is removed therefrom and the metal body quicklychilled either by inserting the same into a bath of cold water, or bydirecting a stream of cold water on to the heated surface.

It will be understood that owing to the character of the heat generatedby a flame of the gases mentioned, the surface of the metal body may beheated to a high temperature in the fraction of a minute and before theheat can penetrate to an undesirable distance beneath the surface, thusleaving the interior of the metal body so far as its chemicalcomposition and condition is concerned, unchanged.

Heretofore surface or case hardening has been confined to wrought ironor steel having a very low per cent. of carbon and which was thereforenot capable of being tempered. By my method, metals that are subject totempering or hardening, may be surface hardened, but which if treated bythe ordinary tempering methods, consisting of heating in a temperingflame and chilling, would result in hardenlng throughout the body. Itwill thus be seen that my improved process not only leaves the interiorof the metal body in its normal condition, or in the conof the surfaceof heating, but it admitsa metal body being hard le ened to the desireddepth within such a;

short period of time, as to produce a great savlng in time, labor andexpense.

What I claim, is- 1. A process for surface hardening iron and steelcontaining a necessaryfper cent. of

carbon, consistin first, in sub ecting the surface to be har ened to theheat from the flame of gas or combined gases at a temperature of over4000 degrees Fahrenheit, second, discontinuing the application of theheat before the body of metal is heated beyond=the depth of metal to behardened, and third, quickly subjecting said heated surface to achilling process.

2. A process for surface hardemng metal containing the necessaryhardening in.- gredients consisting, first, in subjecting'the surfacemetal to be hardened to the action of a heat sufliciently intense vtorapidly bring the surface metal to a hardening temperature before thesub-surface metal has been so affected; second, discontinuing theapplication of heat and subjecting the heated surface metal to a rapidchilling process While at the hardening temperature.

3. A process for surface hardening metal containing the necessaryhardening ingredients consisting, first, in subjecting the surface metalto be hardened to a flame of iron melting intensity, second,discontinuing the heating process as soon as the surface metalhasreached the hardening temperature and before the sub-surface metal hasbeen so affected and applying a rapid chilling process to the surfacemetal While at the hardening temperature.

In testimony whereof I affix my signature in presence of two Witnesses.

JOHN H. MCCORMICK.

Witnesses:

C. C. SHEPHERD, A. L. PHELPS. V

